The present invention relates to integrated circuit technology. More particularly, the present invention relates to imager integrated circuits and to multi-color-channel integrated circuits, and to methods for classifying and correcting vertical color image sensor defects utilizing all color channel information of each defective pixel.
Defects are well known issues in CMOS color image sensors including both vertical color sensors such as the X3 sensor manufactured and marketed by Foveon, Inc., of San Jose, Calif., as well as traditional types of color image sensors. Defects are a cost issue as they negatively affect the yield at various steps of manufacturing. Sensor defects include pixel clusters in the image sensor sharing a common defect in one or more integrated circuit layers, particles on the die surface, and window defects. Prior-art methods have been used to detect defects but have minimal classification capabilities.
Defects are a cost issue as they affect the yield at various steps of manufacturing. Defects can be introduced during different phases of the manufacturing flow, including integrated circuit fabrication, glass manufacturing, and sensor assembly.
Traditional testing for defects does not employ defect classification. During the testing phase of image sensor manufacturing, defect tests are implemented. Sensors having defects that are too large and/or too numerous are rejected. The size and quantity of defects are the main characteristics of defects with this traditional type of testing. Information that is useful for yield enhancement or defect correction is limited with the prior-art approach.
Defect classification presents several challenges. Identifying the different types of defects is a challenge for the testing phase of manufacturing for multiple reasons. There are numerous types of pixel clusters that share many of the same traits. Particles on the die surface are hard to distinguish from some types of pixel cluster defects. Window defects are hard to distinguish from die surface particles and from some types of pixel cluster defects.